To date, most two-dimensional conjugated metal–organic frameworks (2D c-MOFs) are based on planar polycyclic aromatic hydrocarbons (PAHs), which limits the ability to introduce additional substituents to control their properties.
This thesis introduces a novel monomer ligand derived from highly substituted, core-twisted hexahydroxy-hexa-cata-benzocoronenes (6X-6OH-cHBCs), resulting in a new class of wavy 2D c-MOFs. The structural rigidity and self-complementary nature of the c-HBC ligand makes it a valuable monomer for constructing these novel 2D c-MOFs. Despite the wavy structure, effective conjugation between layers was achieved. This led to the formation of electronically conductive materials, as demonstrated by 6F-cHBC-Cu, which exhibited a conductivity of 1.82∙10-2 S/cm. Furthermore, the wavy motif of the c-HBC ligand promoted extended crystal growth in the z-direction. This was demonstrated by the formation of several micrometer-long single crystals of 6F-cHBC-Cu.
The monomers were synthesized through a flexible three-step process, allowing for the incorporation of various substituents or functional groups, thus enabling control over ligand symmetry. This process enabled the synthesis of monomers with diverse symmetries: C6 symmetry (12OH-cHBC), C3 symmetry (6X-6OH-cHBC), and asymmetric monomers (e.g., 3F-6OH-cHBC). This structural variety allowed for systematic investigations into structure-property relationships, offering valuable insights into how monomer design influences the resulting MOF properties. The homologous 6X-cHBC-Cu MOF series (X = H, F, Cl, Br) illustrated that both the electron-withdrawing effect and the size of the substituent significantly impact crystallinity. This in turn enhances fundamental properties such as electronic conductivity, charge carrier mobility, accessible pore size, thermal stability, and morphology. Reactivity trends for the synthesized monomers were also established, showing that strong electron-withdrawing groups like fluorine or hydroxyl directly correlate with enhanced monomer reactivity, optimizing synthetic conditions. Incorporating fluorine into the monomer structure significantly improved the resulting MOF properties, providing a valuable design strategy for future monomers.
Finally, this research demonstrated that wavy 2D c-MOFs can rival traditional flat ligands in terms of crystallinity and electronic properties, such as conductivity and charge carrier mobility, thereby expanding the potential for novel 2D c-MOF members.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:92289 |
| Date | 10 July 2024 |
| Creators | Jastrzembski, Kamil |
| Contributors | Feng, Xinliang, Baek, Jong- Beom, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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